Optimal phasing of charges in a perforating system and method

ABSTRACT

An optimal perforating gun method for accurate perforation in a deviated/horizontal wellbore is disclosed. The method includes a gun string assembly (GSA) deployed in a wellbore with shaped charges arranged in rows in a cluster and a total number of the shaped charges is equal to a total number of the rows. A total number of charges for each cluster in a stage is selected with the best statistical probability for a desired number of perforations in the cluster. The number of charges and the number of rows per each cluster in a stage is optimized such that there is a maximum probability of perforating into a low compression region in an upward and downward direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of U.S. application Ser. No.15/080,251, filed Mar. 24, 2016, the disclosure of which is fullyincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to perforation guns that areused in the oil and gas industry to explosively perforate well casingand underground hydrocarbon bearing formations, and more particularly toarranging shaped charges in rows in a cluster for explosivelyperforating a well casing and its surrounding underground hydrocarbonbearing formation.

PRIOR ART AND BACKGROUND OF THE INVENTION Prior Art Background

During a well completion process, a gun string assembly is positioned inan isolated zone in the wellbore casing. The gun string assemblycomprises a plurality of perforating guns coupled to each other eitherthrough tandems or subs. The perforating gun is then fired, creatingholes through the casing and the cement and into the targeted rock.These perforating holes connect the rock holding the oil and gas and thewell bore. “During the completion of an oil and/or gas well, it iscommon to perforate the hydrocarbon containing formation with explosivecharges to allow inflow of hydrocarbons to the well bore. These chargesare loaded in a perforation gun and are typically shaped charges thatproduce an explosive formed penetrating jet in a chosen direction” U.S.Pat. No. 7,441,601.

Hydrocarbon fracturing tunnels have certain preferred orientations wherethe effectiveness of extracting oil/gas is greatest i.e., when aperforation is aligned along the tunnels, oil/gas flows though theperforation tunnels without taking an alternate path that may become arestrictive path creating high tortuosity conditions.

It has been shown in studies that the fractures initiate close to thewellbore casing in an upward and downward direction. FIG. 1 (0100)generally illustrates a top view of a horizontal drilling pad (0104)within the metes and bounds of a lease or ownership. Multiple horizontalwells (0102) are generally drilled from a vertical well head (0101).Studies have shown that preferred fracturing planes (0103) aretransversely perpendicular to the orientation of the horizontal wellborecasings. Multiple preferred fracturing planes that are parallel to eachother may be targeted for maximum production efficiency. However,horizontal wellbores are often deviated as much as 100 ft in anydirection over the length of 3 miles. Therefore, the orientation of thegun may not be horizontal and is often at an angle. The charges in thegun may or may not be optimally phased when perforating. Field resultsindicate that there is a single dominant perforation tunnel per stage.As there are multiple stages per well, multiple clusters per stagetypically 3 to 15 and multiple perforating guns in each clustertypically 4-6, there is a need for an optimal phasing of the charges ineach of the perforating guns per cluster so that the chances ofperforating in the dominant channel is increased. A cross section of thehorizontal wellbore casing (0207) drilled in a wellbore (0206) isfurther illustrated in FIG. 2 (0200). Due to the compression of rock(0205) from the surface, the hydrocarbon formation is pressed downwardlyand the region proximal to the hydrocarbon formation has adiscontinuity. The discontinuity creates a stress (0204) distributionaround the wellbore. Studies from rock mechanics have indicated a highcompression region (0201) about the sides and a low compression region(0203) around the upward and downward region. Therefore, there is a needto phase the charges to perforate in the low compression region (0202)so that fractures initiate in the low compression region for maximumfracture efficiency. There is a need to phase the charges so that thechances of placing a perforation tunnel in the effective regions of lowcompressive stress are improved. There is a need for the fracture toinitiate at the top and bottom first that has the least principal stressso that there is enough flow rate to propagate the fracture. There is aneed for a perforating gun that perforates such that the fracturepermeates radially to the direction of the wellbore in an upward anddownward direction.

By design, each perforation is expected to be involved in the fracturetreatment. If all perforations are involved, and the perforations areshot with 0°, 60°, 90°, 120°, or 180° phasing, multiple fracture planesmay be created, leading to substantial near wellbore friction anddifficulty in placing the planned fracturing treatment. Field resultsindicate that there is a single dominant perforation tunnel per stage.Therefore, there is a need for minimal multiple fracture initiationsthat do not create ineffective fracture planes. Various prior artphasing in a perforating gun (0302) in a well casing (0301) isillustrated in FIG. 3. For example, FIG. 3 (0310) illustrates a 0°phasing where all the charges are phased to perforate in a downwardlydirection. Similarly, FIG. 3 (0320) illustrates a 0°-180° phasingwherein charges are phased to perforate in an upward and downwarddirection. However, the chances of perforating in an upward and downwarddirection are low when the well casing is deviated and the perforatinggun is not horizontal. There is an accuracy issue of positioning theguns (orienting) with respect to the up/down vector. Field resultsindicate that even with orientation of the guns, operational issues cancause perforations in a non-preferred region. The probability ofperforating in the preferred upward and downward low compression regionis very low for a 0° phasing or a 0°-180° phasing gun.

FIG. 4 further illustrates a perforating gun (0401) with a 0°-180°phasing wherein charges (0404) are phased to perforate in an upward anddownward direction. As illustrated in FIG. 4 (0410) the charges (0404)are perfectly aligned to the preferred direction (0402) and the fracturetreatment through the perforations may produce efficiently. However,since the wells are not perfectly horizontal and in most case deviated,the gun (0411) may be rotated as illustrated in FIG. 4 (0420) and thecharges (0404) may be perforating into the high compression region orsideways and produce ineffective fracture treatment. Therefore, it isimportant to perforate to improve the probability of placing theperforations in the low compression region which are determined to be onthe upward and downward directions.

FIG. 3 (0330) illustrates a 120° phasing wherein 3 charges are phased at120° to perforate. The probability of perforating within 240° of theupward and downward low compression region is 100%. The chances aredecreased to 50% for perforating within 120° and further decreased to25% for perforating within 60° and further decreased to 12.5% forperforating within 30° of the upward and downward low compression regionis 100%. Therefore, there is a need to improve the probability to atleast 80% for perforating within 30° of the upward and downward lowcompression region.

FIG. 3 (0340) illustrates a 90° phasing wherein 4 charges are phased at90° to perforate. The probability of perforating within 90° of theupward and downward low compression region is 100%. The chances aredecreased to 50% for perforating within 90° and further decreased to 25%for perforating within 45°. Therefore, there is a need to place andphase the charges within in a cluster such that the chances ofperforating in the preferred low compression region is at least 75%.

FIG. 3 (0350) illustrates a 60° phasing wherein 6 charges are phased at60° to perforate into a hydrocarbon formation. Prior art perforatingguns are generally loaded with 6 shots per foot (SPF) at 60 degreephasing. With the 60° phasing, the probability of perforating within 60°of the upward and downward low compression region is 100%. Theprobability of perforating within 30° of the upward and downward lowcompression region is 50%. Even with a double shot at the same phasing,the probability remains the same but requires 12 shots spanning 2 feet.Therefore, there is a need to improve the probability to at least 800%for perforating within 30° of the upward and downward low compressionregion (perforation angle).

Currently, 1 to 12 perforation holes per stage are shot which willreconnect to the predominant fracturing plane during fracturingtreatment. Most stages are completed with 6 shots per cluster and 6shots per foot (“spf”) and at 60 degrees for obvious statisticalreasons. Some of the perforation tunnels cause energy and pressure lossduring fracturing treatment which reduces the intended pressure in thefracture tunnels. For example, if a 100 bpm (barrels per minute)fracture fluid is pumped into each fracture zone at 10000 PSI with anintention to fracture each perforation tunnel at 2-3 bpm, most of theenergy is lost in ineffective fractures that have higher tortuosityreducing the injection rate per fracture to substantially less than 2-3bpm. Consequently, the extent of fracture length is significantlyreduced resulting in less oil and gas flow during production. Therefore,there is a need for a system to achieve the highest and optimalinjection rate per perforation tunnel so that a maximum fracture lengthis realized. The more energy put through each perforation tunnel, themore fluid travels through the preferred fracturing plane, the furtherthe fracture extends. Ideally, 1000 feet of fracture length from thewellbore is desired. Therefore, there is a need to get longer extensionof fractures which have minimal tortuosity. For example, in order toachieve 2 bpm in each perforation tunnel, a total injection rate of 100bpm at 1000 psi for 48 perforation tunnels requires 12 clusters eachwith 4 charges. Therefore, there is a need to shoot more zones with 4perforating holes in each cluster that are oriented 2 up and 2 down.Active orientation systems commonly used such as 0 degrees or 180 degreeorientations, have an accuracy of orientation that is estimated to be+−20 degrees with an external orientation and +− with an internalorientation. There is a need to improve the chances of proper placementwithout an active orientation system.

Perforation and fracturing are based on the premise that everyperforation will be in communication with a hydraulic fracture and willbe contributing fluid during the treatment at the pre-determined rate.Therefore, if any perforation does not participate, then the incrementalrate per perforation of every other perforation is increased, resultingin higher perforation friction. Therefore, there is a need to angle andspace charges to facilitate the fracturing process to achieve maximumproduction efficiency.

Prior art U.S. Pat. No. 7,303,017A discloses “a method includesarranging shaped charges in a perforating gun to produce perforationholes in a helical pattern that is defined in part by a phase angle; andchoosing four adjacent perforation holes to be created that are adjacentnearest neighbors. The distances are determined between three of thefour adjacent perforation holes to be created. A standard deviation isminimized between the three adjacent perforation holes. The phase angleis set based on the minimization.” However, U.S. Pat. No. 7,303,017Adoes not teach an optimal phasing of the charges in the bank so thatcharges perforate within desired perforation angles in a low compressionregion especially for a deviated well.

Deficiencies in the Prior Art

The prior art as detailed above suffers from the following deficiencies:

-   -   Prior art perforation phasing systems do not provide for        efficiently reducing tortuosity and energy loss in a perforation        tunnel with minimum number of shots per foot.    -   Prior art perforation phasing systems do not provide for longer        extension of fractures which have minimal tortuosity with        minimum number of shots per foot.    -   Prior art perforation phasing systems do not provide for the        highest and optimal injection rate per perforation tunnel so        that a maximum fracture length is realized with minimum number        of shots per foot in a cluster.    -   Prior art perforation phasing systems do not provide for        achieving a probability greater than 50% for perforating within        +−15° of the upward and downward low compression region.    -   Prior art perforation phasing systems do not provide for an        optimal phasing of the charges in the perforating gun per        cluster in order to achieve maximum perforation and fracturing        efficiency.    -   Prior art perforation phasing systems do not have an optimal        statistical chance of perforation placement when less than or        more than 6 shots are placed in a cluster.

While some of the prior art may teach some solutions to several of theseproblems, the core issue of reacting to unsafe gun pressure has not beenaddressed by prior art.

OBJECTIVES OF THE INVENTION

Accordingly, the objectives of the present invention are (among others)to circumvent the deficiencies in the prior art and affect the followingobjectives:

-   -   Provide for efficiently reducing tortuosity and energy loss in a        perforation tunnel with minimum number of shots per foot.    -   Provide for longer extension of fractures which have minimal        tortuosity with minimum number of shots per foot.    -   Provide for the highest and optimal injection rate per        perforation tunnel so that a maximum fracture length is realized        with minimum number of shots per foot in a cluster.    -   Provide for improving the probability to at least 50% for        perforating within +−15° of the upward and downward low        compression region.    -   Provide for an optimal phasing of the charges in the perforating        gun per cluster in order to achieve maximum perforation and        fracturing efficiency.    -   Provide for perforation phasing systems that have an optimal        statistical chance of perforation placement when less than or        more than 6 shots are placed in a cluster.

While these objectives should not be understood to limit the teachingsof the present invention, in general these objectives are achieved inpart or in whole by the disclosed invention that is discussed in thefollowing sections. One skilled in the art will no doubt be able toselect aspects of the present invention as disclosed to affect anycombination of the objectives described above.

BRIEF SUMMARY OF THE INVENTION System Overview

The present invention in various embodiments addresses one or more ofthe above objectives in the following manner. The present inventionprovides a system that includes an optimal phasing perforating phasedgun system and method for accurate perforation in a deviated/horizontal.The system/method includes a gun string assembly (GSA) deployed in awellbore with shaped charges in clusters. Within a cluster, the chargesare separated into individual banks with a phase angle between thecharges in each bank and an offset angle between banks. The number ofcharges per cluster, the phase angle and the offset angle are optimizedsuch that there is a maximum probability of perforating into a lowcompression region in an upward and downward direction. The fracturetreatment through the perforations in the low compression regions createminimal tortuosity paths for longer extension of fractures that enablesefficient oil and gas flow rates during production.

Method Overview

The present invention system may be utilized in the context of anoverall optimal phasing perforating method, wherein the phasedperforating gun as described previously is controlled by a method havingthe following steps:

-   -   (1) selecting a gun system for each cluster in a stage with the        best statistical probability for the desired number of        perforations in that cluster;    -   (2) positioning a phased perforating gun system in a wellbore        casing; and    -   (3) perforating through the phased perforating gun system into a        hydrocarbon formation such that at least one of the first        plurality of charges and at least one of the second plurality of        charges perforate within a upward perforation angle and a        downward perforation angle; the upward perforation angle        subtends in an upward direction about a center of the        perforating gun and the downward perforation angle subtends in a        downward direction about the center of the perforating gun.

Integration of this and other preferred exemplary embodiment methods inconjunction with a variety of preferred exemplary embodiment systemsdescribed herein in anticipation by the overall scope of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the advantages provided by the invention,reference should be made to the following detailed description togetherwith the accompanying drawings wherein:

FIG. 1 is a top view of a horizontal drilling pad with multiplehorizontal wells that are drilled from a vertical well head.

FIG. 2 is a cross section of the horizontal wellbore casing drilled in awellbore in FIG. 1.

FIG. 3 illustrate various prior art phasing in a perforating gun in awell casing.

FIG. 4 illustrates a perforating gun with a 0°-180° phasing of thecharges.

FIG. 5 shows an end view of a perforating gun illustrating an upwardperforation angle and a downward perforation angle.

FIG. 6 generally illustrates a side perspective view of two chargesphased in a perforating gun defining a phase angle and charge spacing.

FIG. 7A illustrates an exemplary 8-shot (charges) 2-bank, phased at 90°phase angle between charges in each bank, phased 45° offset anglebetween banks in a perforating gun according to a preferred embodimentof the present invention.

FIG. 7B illustrates an exemplary 8-shot (charges) 2-bank, phased at 90°phase angle between charges in each bank, phased 45° offset anglebetween banks in a perforating gun according to a preferred embodimentof the present invention.

FIG. 7C illustrates an exemplary 8-shot (charges) 2-bank non-converging,phased at 90° phase angle between charges in each bank, phased 45°offset angle between banks in a perforating gun according to a preferredembodiment of the present invention.

FIG. 7D illustrates an exemplary cross section view of 8-shot (charges)2-bank, phased at 90° phase angle between charges in each bank, phased45° offset angle between banks with a orienting reference point in aperforating gun according to a preferred embodiment of the presentinvention.

FIG. 8 illustrates an exemplary 12-shot (charges) 3-bank, phased at 120°phase angle between charges in each bank, phased 30° offset anglebetween banks in a perforating gun according to a preferred embodimentof the present invention.

FIG. 9A illustrates an exemplary 6-shot (charges) 2-bank, phased at 120°phase angle between charges in each bank, phased 60° offset anglebetween banks in a perforating gun according to a preferred embodimentof the present invention.

FIG. 9B illustrates an exemplary 6-shot (charges) 2-bank non-converging,phased at 120° phase angle between charges in each bank, phased 60°offset angle between banks in a perforating gun according to a preferredembodiment of the present invention.

FIG. 10A illustrates an exemplary 6-shot (charges) 3-bank, phased at180° phase angle between charges in each bank, phased 90° offset anglebetween banks in a perforating gun according to a preferred embodimentof the present invention.

FIG. 10B illustrates an exemplary 6-shot (charges) 3-banknon-converging, phased at 180° phase angle between charges in each bank,phased 90° offset angle between banks in a perforating gun according toa preferred embodiment of the present invention.

FIG. 11A illustrates an exemplary 10-shot (charges) 2-bank, phased at72° phase angle between charges in each bank, phased 36° offset anglebetween banks in a perforating gun according to a preferred embodimentof the present invention.

FIG. 11B illustrates an exemplary 10-shot (charges) 2-banknon-converging, phased at 72° phase angle between charges in each bank,phased 36° offset angle between banks in a perforating gun according toa preferred embodiment of the present invention.

FIG. 12A illustrates an exemplary 12-shot (charges) 2-bank, phased at60° phase angle between charges in each bank, phased 30° offset anglebetween banks in a perforating gun according to a preferred embodimentof the present invention.

FIG. 12B illustrates an exemplary 12-shot (charges) 2-banknon-converging, phased at 60° phase angle between charges in each bank,phased 30° offset angle between banks in a perforating gun according toa preferred embodiment of the present invention.

FIG. 13A illustrates an exemplary 12-shot (charges) 3-bank, phased at90° phase angle between charges in each bank, phased 30° offset anglebetween banks in a perforating gun according to a preferred embodimentof the present invention.

FIG. 13B illustrates an exemplary 12-shot (charges) 3-banknon-converging, phased at 90° phase angle between charges in each bank,phased 30° offset angle between banks in a perforating gun according toa preferred embodiment of the present invention.

FIG. 14A illustrates an exemplary 12-shot (charges) 4-bank, phased at120° phase angle between charges in each bank, phased 15° offset anglebetween banks in a perforating gun according to a preferred embodimentof the present invention.

FIG. 14B illustrates an exemplary 12-shot (charges) 4-banknon-converging, phased at 120° phase angle between charges in each bank,phased 15° offset angle between banks in a perforating gun according toa preferred embodiment of the present invention.

FIG. 15A illustrates an exemplary 14-shot (charges) 2-bank, phased at51.42° phase angle between charges in each bank, phased 25.5° offsetangle between banks in a perforating gun according to a preferredembodiment of the present invention.

FIG. 15B illustrates an exemplary 14-shot (charges) 2-banknon-converging, phased at 51.42° phase angle between charges in eachbank, phased 25.5° offset angle between banks in a perforating gunaccording to a preferred embodiment of the present invention.

FIG. 16A illustrates an exemplary 16-shot (charges) 4-bank, phased at90° phase angle between charges in each bank, phased 11.25° offset anglebetween banks in a perforating gun according to a preferred embodimentof the present invention.

FIG. 16B illustrates an exemplary 16-shot (charges) 4-banknon-converging, phased at 90° phase angle between charges in each bank,phased 11.25° offset angle between banks in a perforating gun accordingto a preferred embodiment of the present invention.

FIG. 17 illustrates a detailed flowchart of a preferred exemplaryoptimal phasing perforation method with shaped charges according topreferred exemplary invention embodiments.

FIG. 18 illustrates 4 charges arranged in 4 rows in a cluster and 8charges arranged in 8 rows in another cluster according to preferredexemplary invention embodiments

FIG. 19 illustrates a 6-shot, 8-shot and a 12-shot cluster with chargesarranged in rows according to preferred exemplary invention embodiments.

FIG. 20 illustrates a detailed flowchart of a preferred exemplaryperforation method with shaped charges arranged in rows in a clusteraccording to preferred exemplary invention embodiments.

DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS

While this invention is susceptible of embodiment in many differentforms, there is shown in the drawings and will herein be described indetailed preferred embodiment of the invention with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit the broadaspect of the invention to the embodiment illustrated.

The numerous innovative teachings of the present application will bedescribed with particular reference to the presently preferredembodiment, wherein these innovative teachings are advantageouslyapplied to the particular problems of optimal phasing perforating gunsystem and method. However, it should be understood that this embodimentis only one example of the many advantageous uses of the innovativeteachings herein. In general, statements made in the specification ofthe present application do not necessarily limit any of the variousclaimed inventions. Moreover, some statements may apply to someinventive features but not to others.

FIG. 5 (0500) generally illustrates an end view of a wellbore casing(0501). Hereinafter, an “upward perforation angle” (0504) is defined asthe angle subtended in an upward direction (0511) about a center (0510)of the wellbore casing (0501). Similarly, a “downward perforation angle”(0514) is defined as the angle subtended in a downward direction (0512)about a center (0510) of the wellbore casing (0501). It has beenreported that prior art perforating gun phasing achieve an accuracywithin an upward perforation angle (0503) and a downward perforationangle (0513) which are +−75°. Most commonly used systems such as 6 SPFat 60° will place perforation in each 60 degree arc if the 6 shot bankis fully loaded. The chances of placing the perforation in the 60° arcfurther goes down if one shot is left out, i.e., 5 out of 6 shots loadedin a 60° gun. To achieve maximum fracturing efficiency, it is needed toperforate within a preferred upward perforation angle and preferreddownward perforation are +−15° so that the perforation is achieved in anupward low compression region (0505) and a downward low compressionregion (0515). Furthermore, field results as indicated by a dominantperforation hole due to erosion during the fracture treatment have shownthat a dominant tunnel exits on the low side (0515) 70% of the time,high side (0505) 20% of the time, and other sides 10% of time. Thedifferences in the upward and downward production is due to smaller sizeof the perforation hole in the upward direction as compared to the sizeof the perforation hole in the downward direction. The size of theperforation holes are different due to the fact that the perforating gunis closer to the side wall of the casing in the downward direction. Theperforating hole in the downward direction is sometimes twice as largeas the perforating hole in the upward direction. Therefore, there is afurther need to compensate for the disproportionate perforating holesizes by orienting the charges to achieve a 50/50% production from bothupward and downward low compression zones.

FIG. 6 (0600) generally illustrates a side perspective view of twocharges (0602, 0603) phased in a perforating gun (0601). Hereinafter a“phase angle” between two charges may be defined as the angle betweenthe perpendicular lines extending from the charges. For example, angle(0604) defines a phase angle between charge (0602) and charge (0603). Ina 6-shot 6 SPF perforating gun, the phase angle is 60 degrees.Similarly, in a 4-shot perforating gun, the phase angle is 90 degrees.Hereinafter “Charge spacing” may be defined as the spacing between twoconsecutive charges in a perforating gun. For example, charge spacing(0605) may be defined as the spacing between consecutive charges (0602)and (0603).

Preferred Exemplary 8-Shot 2-Bank Phased Perforating Gun System (0700)

An exemplary embodiment of the present invention may be generallyillustrated in FIG. 7A, wherein a phased perforating gun assembly isdeployed inside a wellbore casing along with 2 banks (0700, 0710), eachof the banks comprise plural shaped charges. According to a preferredexemplary embodiment, the angular orientation of the wellbore casing issubstantially horizontal. According to another preferred exemplaryembodiment, the angular orientation of the wellbore casing is deviated.For example, horizontal wellbores are often deviated as much as 100 ftin any direction over the length of 3 miles. Therefore, the angularorientation of the gun may not be horizontal and is often at an anglewith respect to a longitudinal axis of the casing. The charges in thegun may or may not be optimally phased when perforating.

The bank (0700) may comprise charges (0701, 0702, 0703, 0704) and thebank (0710) may comprise charges (0711, 0712, 0713, 0714). The pluralshaped charges in the perforating gun together in bank (0700) and bank(0710) may herein be referred to as “cluster”. Even though four chargeshave been shown in each of the banks in FIG. 7A, the banks may comprisemore than 2 four shaped charges according to a preferred exemplaryembodiment.

Referring to FIG. 7A, the perforating gun may include shaped chargesthat extend around a central axis of the gun in a helical, or spiral,pattern. Each shaped charge points radially outwardly toward a wellcasing, and adjacent shaped charge in the spiral pattern are radiallyseparated by a phase angle of 90°. For example, shaped charge 0701 isradially separated to adjacent shaped charge 0702 by a phase angle of90°. Similarly, shaped charge 0711 is radially separated to adjacentshaped charge 0712 by a phase angle of 90°. According to a preferredexemplary embodiment, the phase angle of the shaped charges in a bankmay range from 1° to 359°. According to a more preferred exemplaryembodiment, the phase angle of the shaped charges in a bank may rangefrom 5° to 90°. According to a most preferred exemplary embodiment, thephase angle of the shaped charges in a bank may range from 15° to 30°.For example, phase angle of the shaped charge 0711 to adjacent shapedcharge 0712 may range from 1° to 359°. According to yet anotherpreferred exemplary embodiment, the phase angle of one bank may be equalto the phase angle of another bank in the cluster. According to yetanother, preferred exemplary embodiment, the phase angle of one bank maybe unequal to the phase angle of another bank in the cluster. Accordingto another preferred exemplary embodiment, the shaped charges areequally spaced. For example, the charge spacing between consecutiveshaped charges (0701), (0702) and (0703) may be equal. According to yetanother preferred exemplary embodiment, the shaped charges are notequally spaced.

According to a preferred exemplary embodiment, the number of charges ineach of the banks may range from 2 to 24. According to a more preferredexemplary embodiment, the number of charges in each of the banks mayrange from 2 to 8. According to a most preferred exemplary embodiment,the number of charges in each of the banks may range from 2 to 6. Forexample, the bank (0700) may comprise 2 to 24 charges and bank (0710)may comprise 2 to 24 charges. According to a preferred exemplaryembodiment, the offset angle ranges from 1 to 90°. According to a morepreferred exemplary embodiment, the offset angle of the shaped chargesbetween the banks may range from 10° to 45°. According to a mostpreferred exemplary embodiment, the offset angle of the shaped chargesbetween the banks may range from 15° to 30°. The offset angle may be thephase angle between charge 0701 and charge 0711. The offset anglebetween 0702 and 0712 would be same if the phase angles of charges inboth the banks are the same. In the illustration shown in FIG. 7A, theoffset angle is 45°. In this example, the offset angle between charges0701 and 0711 is 45°. The offset angle may range from 1° to 90°depending on the required upward and downward perforation angles.

In the illustration presented in FIG. 7A with 4 charges per bank at a90° phase angle between charges and a 45° offset angle (“offset phaseangle”) between banks 0700 and 0710, the probability of perforatingwithin a 45° upward perforation angle is 100%. Similarly, theprobability of perforating within a 22.5° upward perforation angle is50%. In contrast, for a prior art 8 charge system with a 90° phase anglebetween charges, the probability of perforating within a 45° upwardperforation angle is 50% as compared to the exemplary 2 bank 8 chargesystem illustrated in FIG. 7A. An offset angle between each of the banksincreases the probability of shaped charges perforating within a desiredperforation angle so that fractures initiate in the low compressionregion for achieving maximum fracture efficiency. According to apreferred exemplary embodiment, a perforation angle within 30° with aprobability greater than 75% is achieved.

The offset angle, also referred to as offset phase angle, between twobanks may also be achieved by physically rotating one bank with respectto the other bank. As illustrated in FIG. 7D (0760), bank 0700 may behorizontally oriented with four charges at 90° phase angle and bank 0700may be horizontally oriented with four charges at 90° phase angle. Thereference orienting point (0761) may be the same. In this case theoffset angle is zero. The bank 0710 may be physically rotated or twistedby the amount of the desired offset angle with a rotating means about areference point (0761). The configuration of the banks 0700 and 0710after rotating bank 0710 is generally illustrated in FIG. 7D (0770).When the perforating guns are deployed into a well casing, the guns maybe connected to each other via a sub or a tandem (0790). The guns may betwisted or rotated about an orienting reference point (0761) with anywidely available twisting means or mechanism such as ball bearings orthreads or screws. The banks may be rotated about the referenceorienting point (0761) to achieve a desired offset angle. Alternatively,the orienting reference point may be the same for all banks, but thedesired offset angle may be achieved by phasing the charges in each ofthe banks as generally illustrated in FIG. 7A.

One of the banks within the cluster may be at the best orientation andtherefore be the dominant bank within the cluster. The clusters willalso be balanced as each cluster in a stage will have a statisticalprobability of having a bank with charges phased to perforate within anarc in the low compression zone. For example, referring to FIG. 7A, bank(0700) comprising charges (0701, 0702, 0703, 0704) may be the dominantbank while bank (0710) comprising charges (0711, 0712, 0713, 0714) maybe the non-dominant bank. In this case, charge 0701 may be perforatingupwards into the low compression zone within a 45° upward perforationangle with a probability of 100%. Similarly, charge 0703 may beperforating downwards into the low compression zone within a 45°downward perforation angle with a probability of 100%. Alternatively,bank (0710) may be the dominant bank and charges 0711 and 0714 may bethe upward charges perforating into the low compression region andcharges 0712 and 0713 may be the downward charges perforating into thelow compression region. According to a preferred exemplary embodimentthe downward perforation angle and the upward perforation angle mayrange from 1° to 45°. According to a preferred exemplary embodiment,within a stage, the phasing of the charges in the dominant bank in onecluster may be different than the phasing of the charges in the dominantbank in another cluster. Variations in placement of perforation tunnelswith respect to low compression stress areas contributes to variation in“cluster perforation quality”. A variation in cluster perforationquality may imply some clusters in a stage will be treated unequally.For example, a bank similar to bank 0700 may be the dominant bank in onecluster and a bank similar to bank 0710 with a different phasing ofcharges may be the dominant bank in another cluster of the same stage.The advantages of having two different dominant banks with differentphasings (phase angles) in two different clusters enables fracturingfluids to be distributed evenly without competing. In contrast, if thedominant banks with similar phasings in different clusters are treated,fracturing fluids may be dominated by the first dominant bank whilestarving the other dominant bank in the downstream cluster. According toanother preferred exemplary embodiment, the phasing of the charges inthe dominant bank in one cluster may be same as the phasing of thecharges in the dominant bank in another cluster.

As illustrated in Table 1.0, the number of banks, and charges per bankmay be selected to achieve a desired probability for a perforation anglewithin 30° or any other angle. The combination of charges per bank,number of banks, phase angle and offset angle may be chosen per clusterbased on the diameter of the perforating gun, the length of the gun andthe size of the gun. For example, a 2 foot gun may accommodate 12charges or shots with 1 foot loaded and 1 foot for end connections, a3-ft gun may accommodate 12 shots and a 4-ft gun may accommodate 18shots. A conventional prior art perforating gun is generally loaded with6 shots per foot (SPF) at a 60 degree phasing. With the 60° phasing, theprobability of perforating within 60° arc which includes 60° of theupward and downward low compression region is 100%. The probability ofperforating within 30° of the upward and downward low compression regionis 50%. Even with a double shot at the same phasing, the probabilityremains the same but requires 12 shots spanning 2 feet. However, theprobability substantially doubles with an exemplary configuration thatmay include a 2 bank, 6 charges per bank, 60° phasing, and 30° offsetangle. The probability of perforating within 15° of the upward anddownward low compression region is almost 100%. Therefore, the exemplaryconfigurations illustrated in Table 1.0 provides for a more efficientperforations so that fractures initiate in the low compression regionadjacent to the perforating gun for achieving maximum fractureefficiency. Prior art guns may be loaded at the normal shots per footwith charges loaded at 6 SPF at 60° phasing, 4 SPF at 90° phasing, 5 SPFat 72° phasing and 3 SPF 120° phasing. However, according to anexemplary embodiment, a 10 shot gun may be loaded at nearly 6 SPFdensity or a variable density. According to a preferred exemplaryembodiment, the perforation angle may range from 0° to 30° and/or within+−15°. The upward perforation angle may be substantially the same as thedownward perforation angle if the phase angle is the same for all thecharges within a bank.

The size of the perforation holes are different due to the fact that theperforating gun is closer to the side wall of the casing in the downwarddirection. The perforating hole in the downward direction is sometimestwice as large as the perforating hole in the upward direction.According to a preferred exemplary embodiment, the configurations ofTable 1.0, along with orienting the charges, compensate for thedisproportionate perforating hole sizes to achieve a 50/50% productionflow from both upward and downward low compression zones.

TABLE 1.0 Offset No Of Phase Phase Perforation Perforation PerforationShots Charges Angle Angle Angle with Angle with Angle with in Per No ofin each Between 100% 50% 25% Cluster bank Banks bank Banks probabilityprobability probability 8 4 2 90 45 45 22.5 11.25 10 5 2 72 36 36 18 912 6 2 60 30 30 15 7.5 14 7 2 57.4 28.7 26 13 6.5 15 5 3 57.5 24 24 12 612 4 3 90 30 30 15 7.5

FIG. 7A (0720) generally illustrates phase angle (0721) vs charges(0722) for an unrolled gun. The charges in banks 0700 and 0710 areillustrated along with the phase angle and offset angle. For example,the phase angle (0730) between charge 0701 and charge 0702 is 90°. Theoffset angle (0740) between charge 0701 and charge 0711 is 45°.

According to a preferred exemplary embodiment, the charges in the firstbank and the charges in the second bank may be further angled to placepreferred initiation points on a transverse plane to the wellborecasing. The transverse plane may be perpendicular to the longitudinalaxis of the wellbore casing. The initiation points may or may notintersect with each other, but charges may be oriented such that theinitiation points intersect the preferred fracturing plane so that thefractures created from the initiation points create minimal tortuosityand longer extension of fractures. The initiation points in thepreferred plane are particularly significant for wellbore completions toachieve maximum efficiency during oil and gas production. It has beenknown through several field studies and field data that the preferredplane is transverse about the horizontal direction of the wellborecasing. Initiation points are inherently present in perforation tunnelswhen shaped charges perforate. Not every point in the perforation tunnelis preferred. The preferred initiation points may lie at the end of theclear tunnel (tip) of the perforation tunnels and furthermore thepreferred initiation points lie in a preferred fracturing plane. Afracturing fluid is then pumped at high pressures so that the fracturefluid extends the fractures to the maximum extent in the preferredperforating orientation. The extent of the fracture length extendingradially outward from the wellbore casing may be 1000 feet according toa preferred exemplary embodiment. According to another preferredexemplary embodiment, the charges in at least two of the perforatingbanks are configured to place preferred initiation points on a singletransverse plane to said wellbore casing. According to another preferredexemplary embodiment the charges in at least two of the perforatingbanks are configured to place preferred initiation points on a pluralityof planes. Plurality of planes may be transverse to the wellbore casing.For example, the charges (0701, 0702, 0703, 0704) in bank (0700) may beoriented such that they intersect a first preferred fracturing planewhile charges (0711, 0712, 0713, 0714) in bank (0710) may be orientedsuch that they intersect a second preferred fracturing plane that may besubstantially parallel to the first preferred fracturing plane. Both thefirst preferred fracturing plane and the second preferred fracturingplane are transverse to the longitudinal axis of the wellbore casing.

Preferred Exemplary 8-Shot 2-Bank Phased Perforating Gun System

FIG. 7B illustrates an exemplary 8-shot (charges) 2-bank, phased at 90°phase angle between charges in each bank, phased at a 45° offset anglebetween banks in a perforating gun system according to a preferredembodiment. A cross section view (0750), an end view (0751), and aperspective view (0752) of an exemplary phased gun system is generallyillustrated in FIG. 7B. The system may comprise a first perforating bank(0700) and a second perforating bank (0710) similar to the banksillustrated in FIG. 7A. According to a preferred exemplary embodiment,at least one of the 4 charges in the first perforating bank and at leastone of the 4 charges in the second perforating bank are configured toperforate into a low compression region that is proximal to the wellcasing. According to a further preferred exemplary embodiment, thecharges in the first perforating bank (0700) and second perforating bank(0710) are each oriented such that when the charges perforate, thecharges intersect preferred fracturing planes (0743, 0753) respectively.

Preferred Exemplary 8-Shot 2-Bank Phased Perforating Gun Non-ConvergingSystem

Similar to FIG. 7C, a cross section view (0790), an end view (0791), anda perspective view (0792) of an exemplary phased gun system is generallyillustrated in FIG. 7B. The system may comprise 4 charges phased at a90° phase angle in each of a first perforating bank and a secondperforating bank. The first perforating bank and the second perforatingbank are phased at an offset angle of 45°. The charges may benon-converging and may not be intersecting a preferred fracturing planewhen perforating.

Preferred Exemplary 9-Shot 3-Bank Phased Perforating Gun System (0800)

An exemplary embodiment of the present invention may be generallyillustrated in FIG. 8, wherein a phased perforating gun is deployedinside a wellbore casing along with 3 banks (0800, 0810, 0820), each ofthe banks comprise plural shaped charges. According to a preferredexemplary embodiment, the orientation of the wellbore casing issubstantially horizontal. According to another preferred exemplaryembodiment, the orientation of the wellbore casing is deviated.

The bank (0800) may comprise charges (0801, 0802, 0803), the bank (0810)may comprise charges (0811, 0812, 0813) and the bank (0820) may comprisecharges (0821, 0822, 0823). The plural shaped charges in the perforatinggun together in the bank (0800), the bank (0810) and the bank (0820) mayherein be referred to as “cluster”. Even though three charges have beenshown in each of the banks in FIG. 8, the banks may comprise more than 2shaped charges according to a preferred exemplary embodiment.

Referring to FIG. 8, the perforating gun may include shaped charges thatextend around a central axis of the gun in a helical, or spiral,pattern. Each shaped charge points radially outwardly toward a wellcasing, and adjacent shaped charge in the spiral pattern are radiallyseparated by a phase angle of 120°. For example, shaped charge 0821 isradially separated to adjacent shaped charge 0822 by a phase angle of120°. Similarly, shaped charge 0811 is radially separated to adjacentshaped charge 0812 by a phase angle of 120°.

According to a preferred exemplary embodiment, the offset angle rangesfrom 1 to 90 degrees. According to a more preferred exemplaryembodiment, the offset angle of the shaped charges between the banks mayrange from 10° to 60°. According to a most preferred exemplaryembodiment, the offset angle of the shaped charges between the banks mayrange from 15° to 30°. The offset angle may be the phase angle betweencharge 0801 and charge 0811. The offset angle between 0802 and 0812would be same if the phase angles of charges in both the banks are thesame. In the illustration shown in FIG. 8, the offset angle is 30°. Inthis example, the offset angle between charges 0801 and 0811 is 30°. Theoffset angle may range from 1° to 45° depending on the required upwardand downward perforation angles. According to a preferred exemplaryembodiment, the offset angles between a set of banks may be equal to anoffset angle between a different set of banks. According to a preferredexemplary embodiment, the offset angles between a set of banks may notbe equal to an offset angle between a different set of banks. Forexample, the offset angle between bank 0800 and bank 0810 may bedifferent from the offset angle between bank 0810 and bank 0820. Theoffset angle between bank 0800 and bank 0810 may be the same as theoffset angle between bank 0810 and bank 0820.

In the illustration shown in FIG. 8 with 3 charges per bank at a 120°phase angle between charges and a 30° offset angle between each of thebanks 0800, 0810 and 0820, the probability of perforating within a 30°upward perforation angle is 100%. Similarly, the probability ofperforating within a 15° upward perforation angle is 50%. In contrast,for a prior art 9 charge system with a 45° phase angle between charges,the probability of perforating within a 30° upward perforation angle is75% as compared to the exemplary 3 bank 9 charge system illustrated inFIG. 8. An offset angle between each of the banks increases theprobability of shaped charges perforating within a desired perforationangle so that fractures initiate in the low compression region forachieving maximum fracture efficiency.

FIG. 8 (0830) generally illustrates phase angle (0831) Vs location ofcharges (0832) for an unrolled gun. The charges in banks 0800, 0810 and0820 are illustrated along with the phase angle and offset angle. Forexample, the phase angle (0850) between charge 0801 and charge 0802 is120°. The offset angle (0860) between charge 0801 and charge 0811 is30°.

As illustrated in FIG. 7A, the phase angle of the charges is 90° withtwo oppositely phased charges. For example, charges 0701 and 0702 arephased diametrically opposite to each other. As illustrated in FIG. 8,the phase angle of the charges is 120° with none of the chargesdiametrically opposite to each other. For example, charges 0701 and 0702are phased diametrically opposite to each other 0801, 0802 and 0803 arephased with no two charges diametrically opposite to each other. It ismore preferable to phase charges diametrically opposite to each othersuch as in FIG. 7A so that there is a better probability to perforate inthe arc in a low compression zone upwards and downwards.

Preferred Exemplar 6-Shot 2-Bank Phased Perforating Gun System

FIG. 9A generally illustrates an exemplary 6-shot (charges) 2-bank,phased at 120° phase angle between charges in each bank, phased 60°offset angle between banks in a perforating gun according to a preferredembodiment of the present invention. A cross section view (0900), an endview (0901), and a perspective view (0902) of an exemplary phased gunsystem is generally illustrated in FIG. 9A. The system (0900) maycomprise a first perforating bank (0910) and a second perforating bank(0920). The first perforating bank (0910) comprising 3 charges phased at120° phase angle to each other. Similarly the second perforating bank(0920) comprising 3 charges phased at 120° phase angle to each other.The first perforating bank (0910) and the second perforating bank (0920)are phased at an offset angle of 60°. According to a preferred exemplaryembodiment, at least one of the 3 charges in the first perforating bankand at least the 3 charges in the second perforating bank are configuredto perforate into a low compression region that is proximal to the wellcasing. The low compression region is similar to the upward lowcompression region (0505) and a downward low compression region (0515)described above in FIG. 5. According to a further preferred exemplaryembodiment, the charges in the first perforating bank (0910) areoriented such that when the charges perforate, the charges intersect apreferred fracturing plane (0911). The preferred fracturing plane may betransverse to the orientation of the wellbore casing. Similarly, thecharges in the second perforating bank (0920) are oriented such thatwhen the charges perforate, the charges intersect a preferred fracturingplane (0911). The preferred fracturing plane (0911) and preferredfracturing plane (0921) may be parallel to each other as described abovein FIG. 1 (0103). Multiple preferred fracturing planes that are parallelto each other may be targeted for maximum production efficiency.

Preferred Exemplary 6-Shot 2-Bank Phased Perforating Gun Non-ConvergingSystem

Similar to FIG. 9A, a cross section view (0930), an end view (0931), anda perspective view (0932) of an exemplary phased gun system is generallyillustrated in FIG. 9B. The system (0930) may comprise a firstperforating bank (0940) and a second perforating bank (0950). The firstperforating bank (0940) comprising 3 charges phased at 120° phase angleto each other. Similarly the second perforating bank (0950) comprising 3charges phased at 120° phase angle to each other. The first perforatingbank (0940) and the second perforating bank (0950) are phased at anoffset angle of 60°. The charges may be non-converging and may not beintersecting a preferred fracturing plane when perforating.

Preferred Exemplary 6-Shot 3-Bank Phased Perforating Gun System

FIG. 10A illustrates an exemplary 6-shot (charges) 3-bank, phased at180° phase angle between charges in each bank, phased at a 90° offsetangle between banks in a perforating gun system according to a preferredembodiment. A cross section view (1000), an end view (1001), and aperspective view (1002) of an exemplary phased gun system is generallyillustrated in FIG. 10A. The system (1000) may comprise a firstperforating bank (1010), a second perforating bank (1020) and a thirdperforating bank (1030). According to a preferred exemplary embodiment,at least one of the 2 charges in the first perforating bank, at leastone of the 2 charges in the second perforating bank and at least one ofthe 2 charges in the third perforating bank are configured to perforateinto a low compression region that is proximal to the well casing.According to a further preferred exemplary embodiment, the charges inthe first perforating bank (1010), second perforating bank and thirdperforating bank are each oriented such that when the charges perforate,the charges intersect a preferred fracturing planes (1011, 1021, 1031)respectively.

Preferred Exemplary 6-Shot 3-Bank Phased Perforating Gun Non-ConvergingSystem

Similar to FIG. 10A, a cross section view (1040), an end view (1041),and a perspective view (1042) of an exemplary phased gun system isgenerally illustrated in FIG. 10B. The system may comprise 2 chargesphased at a 180° phase angle in each of a first perforating bank (1050),a second perforating bank (1070) and a third perforating bank (1060).The first perforating bank (1050), the second perforating bank (1070)and the third perforating bank (1060) are phased at an offset angle of90°. The charges may be non-converging and may not be intersecting apreferred fracturing plane when perforating.

Preferred Exemplary 10-Shot 2-Bank Phased Perforating Gun System

FIG. 11A illustrates an exemplary 10-shot (charges) 2-bank, phased at72° phase angle between charges in each bank, phased at a 36° offsetangle between banks in a perforating gun system according to a preferredembodiment. A cross section view (1100), an end view (1101), and aperspective view (1102) of an exemplary phased gun system is generallyillustrated in FIG. 11A. The system (1100) may comprise a firstperforating bank (1110) and a second perforating bank (1120). Accordingto a preferred exemplary embodiment, at least one of the 5 charges inthe first perforating bank and at least one of the 5 charges in thesecond perforating bank are configured to perforate into a lowcompression region that is proximal to the well casing. According to afurther preferred exemplary embodiment, the charges in the firstperforating bank (1110) and second perforating bank (1120) are eachoriented such that when the charges perforate, the charges intersectpreferred fracturing planes (1111, 1121) respectively.

Preferred Exemplary 10-Shot 2-Bank Phased Perforating Gun Non-ConvergingSystem

Similar to FIG. 11A, a cross section view (1150), an end view (1151),and a perspective view (1152) of an exemplary phased gun system isgenerally illustrated in FIG. 11B. The system may comprise 5 chargesphased at a 72° phase angle in each of a first perforating bank (1130)and a second perforating bank (1140). The first perforating bank (1130)and the second perforating bank (1140) are phased at an offset angle of36°. The charges may be non-converging and may not be intersecting apreferred fracturing plane when perforating.

Preferred Exemplary 12-Shot 2-Bank Phased Perforating Gun System

FIG. 12A illustrates an exemplary 12-shot (charges) 2-bank, phased at60° phase angle between charges in each bank, phased at a 30° offsetangle between banks in a perforating gun system according to a preferredembodiment. A cross section view (1200), an end view (1201), and aperspective view (1202) of an exemplary phased gun system is generallyillustrated in FIG. 12A. The system (1200) may comprise a firstperforating bank (1210) and a second perforating bank (1220). Accordingto a preferred exemplary embodiment, at least one of the 6 charges inthe first perforating bank and at least one of the 6 charges in thesecond perforating bank are configured to perforate into a lowcompression region that is proximal to the well casing. According to afurther preferred exemplary embodiment, the charges in the firstperforating bank (1210) and second perforating bank (1220) are eachoriented such that when the charges perforate, the charges intersectpreferred fracturing planes (1211, 1221) respectively.

Preferred Exemplary 12-Shot 2-Bank Phased Perforating Gun Non-ConvergingSystem

Similar to FIG. 12A, a cross section view (1250), an end view (1251),and a perspective view (1252) of an exemplary phased gun system isgenerally illustrated in FIG. 12B. The system may comprise 6 chargesphased at a 60° phase angle in each of a first perforating bank (1230)and a second perforating bank (1240). The first perforating bank (1230)and the second perforating bank (1240) are phased at an offset angle of30°. The charges may be non-converging and may not be intersecting apreferred fracturing plane when perforating.

Preferred Exemplary 6-Shot 3-Bank Phased Perforating Gun System

FIG. 13A illustrates an exemplary 12-shot (charges) 3-bank, phased at90° phase angle between charges in each bank, phased at a 30° offsetangle between banks in a perforating gun system according to a preferredembodiment. A cross section view (1300), an end view (1301), and aperspective view (1302) of an exemplary phased gun system is generallyillustrated in FIG. 13A. The system (1300) may comprise a firstperforating bank (1310), a second perforating bank (1320) and a thirdperforating bank (1330). According to a preferred exemplary embodiment,at least one of the 4 charges in the first perforating bank, at leastone of the 4 charges in the second perforating bank and at least one ofthe 4 charges in the third perforating bank are configured to perforateinto a low compression region that is proximal to the well casing.According to a further preferred exemplary embodiment, the charges inthe first perforating bank (1310), second perforating bank (1320) andthird perforating bank (1330) are each oriented such that when thecharges perforate, the charges intersect a preferred fracturing planes(1311, 1321, 1331) respectively.

Preferred Exemplary 12-Shot 3-Bank Phased Perforating Gun Non-ConvergingSystem

Similar to FIG. 13A, a cross section view (1340), an end view (1341),and a perspective view (1342) of an exemplary phased gun system isgenerally illustrated in FIG. 13B. The system may comprise 4 chargesphased at a 90° phase angle in each of a first perforating bank (1340),a second perforating bank (1350) and a third perforating bank (1360).The first perforating bank (1340), the second perforating bank (1350)and the third perforating bank (1360) are phased at an offset angle of30°. The charges may be non-converging and may not be intersecting apreferred fracturing plane when perforating.

Preferred Exemplary 12-Shot 4-Bank Phased Perforating Gun System

FIG. 14A illustrates an exemplary 12-shot (charges) 4-bank, phased at120° phase angle between charges in each bank, phased at a 15° offsetangle between banks in a perforating gun system according to a preferredembodiment. A cross section view (1400), an end view (1401), and aperspective view (1402) of an exemplary phased gun system is generallyillustrated in FIG. 14A. The system (1400) may comprise a firstperforating bank (1410), a second perforating bank (1420), a thirdperforating bank (1430) and a fourth perforating bank (1440). Accordingto a preferred exemplary embodiment, at least one of the 3 charges inthe first perforating bank, at least one of the 3 charges in the secondperforating bank, at least one of the 3 charges in the third perforatingbank and at least one of the 3 charges in the fourth perforating bankare configured to perforate into a low compression region that isproximal to the well casing. According to a further preferred exemplaryembodiment, the charges in the first perforating bank, secondperforating bank, third perforating bank and fourth perforating bank areeach oriented such that when the charges perforate, the chargesintersect preferred fracturing planes (1411, 1421, 1431, 1441)respectively.

Preferred Exemplary 12-Shot 4-Bank Phased Perforating Gun Non-ConvergingSystem

Similar to FIG. 14A, a cross section view (1490), an end view (1491),and a perspective view (1492) of an exemplary phased gun system isgenerally illustrated in FIG. 14B. The system may comprise 3 chargesphased at 120° phase angle in each of a first perforating bank (1450), asecond perforating bank (1460), a third perforating bank (1470) and afourth perforating bank (1480). The first perforating bank (1450), thesecond perforating bank (1460), the third perforating bank (1470) andthe fourth perforating bank (1480) are phased at an offset angle of 15°.The charges may be non-converging and may not be intersecting apreferred fracturing plane when perforating.

Preferred Exemplary 14-Shot 2-Bank Phased Perforating Gun System

FIG. 15A illustrates an exemplary 14-shot (charges) 2-bank, phased at51.42° phase angle between charges in each bank, phased at a 25.5°offset angle between banks in a perforating gun system according to apreferred embodiment. A cross section view (1500), an end view (1501),and a perspective view (1502) of an exemplary phased gun system isgenerally illustrated in FIG. 15A. The system (1500) may comprise afirst perforating bank (1510) and a second perforating bank (1520).According to a preferred exemplary embodiment, at least one of the 7charges in the first perforating bank and at least one of the 7 chargesin the second perforating bank are configured to perforate into a lowcompression region that is proximal to the well casing. According to afurther preferred exemplary embodiment, the charges in the firstperforating bank (1510) and second perforating bank (1520) are eachoriented such that when the charges perforate, the charges intersectpreferred fracturing planes (1511, 1521) respectively.

Preferred Exemplary 14-Shot 2-Bank Phased Perforating Gun Non-ConvergingSystem

Similar to FIG. 15A, a cross section view (1550), an end view (1551),and a perspective view (1552) of an exemplary phased gun system isgenerally illustrated in FIG. 15B. The system may comprise 7 chargesphased at a 52.2° phase angle in each of a first perforating bank (1530)and a second perforating bank (1540). The first perforating bank (1530)and the second perforating bank (1540) are phased at an offset angle of25.5°. The charges may be non-converging and may not be intersecting apreferred fracturing plane when perforating.

Preferred Exemplary 16-Shot 4-Bank Phased Perforating Gun System

FIG. 16A illustrates an exemplary 16-shot (charges) 4-bank, phased at90° phase angle between charges in each bank, phased at a 11.25° offsetangle between banks in a perforating gun system according to a preferredembodiment. A cross section view (1600), an end view (1601), and aperspective view (1602) of an exemplary phased gun system is generallyillustrated in FIG. 16A. The system (1600) may comprise a firstperforating bank (1610), a second perforating bank (1620), a thirdperforating bank (1630) and a fourth perforating bank (1640). Accordingto a preferred exemplary embodiment, at least one of the 3 charges inthe first perforating bank, at least one of the 3 charges in the secondperforating bank, at least one of the 3 charges in the third perforatingbank and at least one of the 3 charges in the fourth perforating bankare configured to perforate into a low compression region that isproximal to the well casing. According to a further preferred exemplaryembodiment, the charges in the first perforating bank, secondperforating bank, third perforating bank and fourth perforating bank areeach oriented such that when the charges perforate, the chargesintersect preferred fracturing planes (1611, 1621, 1631, 1641)respectively.

Preferred Exemplary 16-Shot 4-Bank Phased Perforating Gun Non-ConvergingSystem

Similar to FIG. 16A, a cross section view (1690), an end view (1691),and a perspective view (1692) of an exemplary phased gun system isgenerally illustrated in FIG. 16B. The system may comprise 3 chargesphased at 90° phase angle in each of a first perforating bank (1650), asecond perforating bank (1660), a third perforating bank (1670) and afourth perforating bank (1680). The first perforating bank (1650), thesecond perforating bank (1660), the third perforating bank (1670) andthe fourth perforating bank (1680) are phased at an offset angle of11.25°. The charges may be non-converging and may not be intersecting apreferred fracturing plane when perforating.

Preferred Exemplary Flowchart Embodiment of an Phasing WellborePerforation (1700)

As generally seen in the flow chart of FIG. 17 (1700), a preferredexemplary optimal phasing perforation method shaped charges may begenerally described in terms of the following steps:

-   -   (1) selecting a gun system for each cluster in a stage with the        best statistical probability for a desired number of        perforations in that cluster (1701);    -   (2) positioning a phased perforating gun in a wellbore casing        (1702); and    -   (3) perforating through the phased perforating gun into a        hydrocarbon formation such that at least one of a first        plurality of charges and at least one of a second plurality of        charges perforate within an upward perforation angle and a        downward perforation angle; the upward perforation angle        subtends in an upward direction about a center of the        perforating gun and the downward perforation angle subtends in a        downward direction about the center of the perforating gun        (1703).

Referring to FIG. 18, a perforating gun may include shaped charges thatextend around a central axis of the gun in a helical, or spiral,pattern. Each shaped charge points radially outwardly toward a wellcasing, and adjacent shaped charge in the spiral pattern are radiallyseparated by a phase angle. FIG. 18 (1810) generally illustrates anunwrapped perforating gun with charges (1811, 1812, 1813, 1814) in acluster that are arranged in rows (1811, 1822, 1823, 1824). Each chargeoccupies a row according to a preferred exemplary embodiment. Forexample each of the charges (1811, 1812, 1813, 1814) occupy the rows(1811, 1822, 1823, 1824) respectively. A 4-shot shot gun may compriseone cluster with 4 charges. It is noteworthy that no two charges occupythe same row as in conventional perforating gun designs. Therefore a4-charge cluster in a perforating gun may occupy 4 rows. Similarly, a8-charge cluster may occupy 8 rows as generally illustrated in FIG. 18(1820). FIG. 19 (1910) generally illustrates a front view of 6-shot guncomprising 6-charges per cluster. Similarly, FIG. 19 (1920) generallyillustrates a front view of 8-shot gun comprising 8-charges per cluster.FIG. 19 (1930) generally illustrates a front view of 12-shot guncomprising 12-charges per cluster. The more the number of charges in acluster arranged in non-overlapping individual rows the more theefficiency of perforation in an upward and downward perforation angle.For example, the 6-shot (1910) has an uncertainty of 50%, the 8-shot(1920) has an uncertainty of 33%, and the 12-shot (1930) has anuncertainty of 0%. The uncertainty may be a measure of the effectivenessof the perforation in an upward and downward direction. To achievemaximum fracturing efficiency, it is needed to perforate within apreferred upward perforation angle and preferred downward perforationwhich are +−15° so that the perforation is achieved in an upward lowcompression region (0505) and a downward low compression region (0515).According to a preferred exemplary embodiment, when perforating throughthe perforating gun system into a hydrocarbon formation, at least one ofthe plurality of charges in the cluster perforate within an upwardperforation angle and at least one of the plurality of charges in thecluster perforate within an a downward perforation angle; the upwardperforation angle subtends in an upward direction about a center of thewellbore and the downward perforation angle subtends in a downwarddirection about the center of the wellbore. According to a preferredexemplary embodiment, the phase angle of the shaped charges in a clustermay range from 1° to 359°. According to a more preferred exemplaryembodiment, the phase angle of the shaped charges in a cluster may rangefrom 5° to 90°. According to a most preferred exemplary embodiment, thephase angle of the shaped charges in a cluster may range from 15° to30°. According to another preferred exemplary embodiment, the shapedcharges are equally spaced. For example, the charge spacing betweenconsecutive shaped charges (1811), (1812), (1813) and (1814) may beequal. According to yet another preferred exemplary embodiment, theshaped charges are not equally spaced.

According to a preferred exemplary embodiment, the number of charges ineach of the clusters may range from 2 to 24. According to a morepreferred exemplary embodiment, the number of charges in each of theclusters may range from 2 to 8. According to a most preferred exemplaryembodiment, the number of charges in each of the clusters may range from2 to 6. For example, the cluster (1810) may comprise 4 charges andcluster (1820) may comprise 8 charges.

The number of charges in each of the clusters may be balanced as eachcluster in a stage will have a statistical probability of having acluster with charges phased to perforate within an arc in the lowcompression zone. According to a preferred exemplary embodiment thedownward perforation angle and the upward perforation angle may rangefrom 1° to 45°. According to a preferred exemplary embodiment, within astage, the phasing of the charges in one cluster may be different thanthe phasing of the charges in another cluster. Variations in placementof perforation tunnels with respect to low compression stress areascontributes to variation in “cluster perforation quality”. A variationin cluster perforation quality may imply some clusters in a stage willbe treated unequally.

Preferred Exemplary Flowchart Embodiment of an Phasing WellborePerforation (2000)

As generally seen in the flow chart of FIG. 20 (2000), a preferredexemplary perforation method may be generally described in terms of thefollowing steps:

-   -   (1) selecting the total number of said plurality of charges for        the cluster for each of the plurality of perforating guns in a        stage with the best statistical probability for a desired number        of perforations in said cluster (2001);    -   (2) positioning a perforating gun system in a wellbore casing        (2002); and    -   (3) perforating through the perforating gun system into a        hydrocarbon formation such that at least one of said plurality        of charges perforate within an upward perforation angle and at        least one of the plurality of charges perforate within an a        downward perforation angle; the upward perforation angle        subtends in an upward direction about a center of the wellbore        and the downward perforation angle subtends in a downward        direction about the center of the wellbore (2003).

Method Summary

The present invention method anticipates a wide variety of variations inthe basic theme of implementation, but can be generalized as a for usein a wellbore casing operating in conjunction with a perforating gunsystem comprising a plurality of perforating guns; each of the pluralityof perforating guns configured with a plurality of charges; theplurality of charges arranged in a plurality of rows in a cluster; and atotal number of the plurality of charges is equal to a total number ofthe plurality of rows;

wherein the method comprises the steps of:

-   -   (1) selecting the total number of the plurality of charges for        the cluster for each of the plurality of perforating guns in a        stage with the best statistical probability for a desired number        of perforations in the cluster;    -   (2) positioning the perforating gun system in the wellbore        casing; and    -   (3) perforating through the perforating gun system into a        hydrocarbon formation such that at least one of the plurality of        charges perforate within an upward perforation angle and at        least one of the plurality of charges perforate within a        downward perforation angle; the upward perforation angle        subtends in an upward direction about a center of the wellbore        and the downward perforation angle subtends in a downward        direction about the center of the wellbore.

This general method summary may be augmented by the various elementsdescribed herein to produce a wide variety of invention embodimentsconsistent with this overall design description.

System/Method Variations

The present invention anticipates a wide variety of variations in thebasic theme of oil and gas extraction. The examples presented previouslydo not represent the entire scope of possible usages. They are meant tocite a few of the almost limitless possibilities.

This basic system and method may be augmented with a variety ofancillary embodiments, including but not limited to:

-   -   An embodiment wherein the wellbore casing is substantially        horizontal.    -   An embodiment wherein the wellbore casing is deviated.    -   An embodiment wherein the plurality of rows are equally spaced.    -   An embodiment wherein the plurality of rows are unequally        spaced.    -   An embodiment wherein a phase angle of the plurality of charges        ranges from 1 to 359 degrees.    -   An embodiment wherein the upward perforation angle ranges from 0        to 45 degrees.    -   An embodiment wherein the downward perforation angle ranges from        0 to 45 degrees.    -   An embodiment wherein the plurality of charges are further        angled to place preferred initiation points on a transverse        plane to the wellbore casing.    -   An embodiment wherein at least two of the plurality of charges        in each of the plurality of perforating guns are configured to        place preferred initiation points on a single transverse plane        to the wellbore casing.    -   An embodiment wherein at least two of the plurality of charges        in each of the plurality of perforating guns are configured to        place preferred initiation points on a plurality of planes; the        plurality of planes transverse to the wellbore casing.

One skilled in the art will recognize that other embodiments arepossible based on combinations of elements taught within the aboveinvention description.

CONCLUSION

An optimal perforating gun method for accurate perforation in adeviated/horizontal wellbore has been disclosed. The method includes agun string assembly (GSA) deployed in a wellbore with shaped chargesarranged in rows in a cluster and a total number of the shaped chargesis equal to a total number of the rows. A total number of charges foreach cluster in a stage is selected with the best statisticalprobability for a desired number of perforations in the cluster. Thenumber of charges and the number of rows per each cluster in a stage isoptimized such that there is a maximum probability of perforating into alow compression region in an upward and downward direction.

Although a preferred embodiment of the present invention has beenillustrated in the accompanying drawings and described in the foregoingdetailed description, it will be understood that the invention is notlimited to the embodiments disclosed, but is capable of numerousrearrangements, modifications, and substitutions without departing fromthe spirit of the invention as set forth and defined by the followingclaims.

What is claimed is:
 1. A perforating method for use in a wellbore casingoperating in conjunction with a perforating gun system comprising aplurality of perforating guns; each of said plurality of perforatingguns configured with a plurality of charges; said plurality of chargesarranged in a plurality of rows in a cluster; and a total number of saidplurality of charges is equal to a total number of said plurality ofrows; wherein said method comprises the steps of: (1) selecting saidtotal number of said plurality of charges for said cluster for each ofsaid plurality of perforating guns in a stage with the best statisticalprobability for a desired number of perforations in said cluster; (2)positioning said perforating gun system in said wellbore casing; and (3)perforating through said perforating gun system into a hydrocarbonformation such that at least one of said plurality of charges perforatewithin an upward perforation angle and at least one of said plurality ofcharges perforate within a downward perforation angle; said upwardperforation angle subtends in an upward direction about a center of saidwellbore casing and said downward perforation angle subtends in adownward direction about said center of said wellbore casing.
 2. Theperforating method of claim 1 wherein said wellbore casing issubstantially horizontal.
 3. The perforating method of claim 1 whereinsaid wellbore casing is deviated.
 4. The perforating method of claim 1wherein said plurality of rows are equally spaced.
 5. The perforatingmethod of claim 1 wherein said plurality of rows are unequally spaced.6. The perforating method of claim 1 wherein a phase angle of saidplurality of charges ranges from 1 to 359 degrees.
 7. The perforatingmethod of claim 1 wherein said upward perforation angle ranges from 0 to45 degrees.
 8. The perforating method of claim 1 wherein said downwardperforation angle ranges from 0 to 45 degrees.
 9. The perforating methodof claim 1 wherein said plurality of charges are further angled to placepreferred initiation points on a transverse plane to said wellborecasing.
 10. The perforating method of claim 1 wherein at least two ofsaid plurality of charges in each of said plurality of perforating gunsare configured to place preferred initiation points on a singletransverse plane to said wellbore casing.
 11. The perforating method ofclaim 1 wherein at least two of said plurality of charges in each ofsaid plurality of perforating guns are configured to place preferredinitiation points on a plurality of planes; said plurality of planestransverse to said wellbore casing.